1. Field of the Invention
The present invention relates to an image processing apparatus and a camera apparatus that execute signal processing for performing, on an image signal produced by imaging with one of various kinds of camera systems, an automatic exposure control that is adapted to imaging an object having a wide dynamic range, as well as to an automatic exposure control method for these apparatuses.
2. Description of the Related Art
A camera system is known in which a DSP (digital signal processor) performs signal processing, such as color separation, on a received image signal that is obtained by an imaging device and an automatic exposure control is performed on the imaging device by using an integration value of a luminance signal that is calculated by an OPD (optical detector) section of the DSP.
Incidentally, when shooting is performed with such a camera system in a backlight state, for example, a wide-dynamic-range image including both high-luminance objects and low-luminance objects, for example, is to be processed.
In this case, the following two methods are conceivable as an exposure control method of the conventional camera system:
(1) An exposure control is performed in such a manner as to be adjusted to the high-luminance objects; and
(2) An exposure control is performed in such a manner as to be adjusted to the low-luminance objects.
However, method (1) has a problem that blackening occurs for the low-luminance objects because of an insufficient quantity of light. In method (2), the white levels of the high-luminance objects become unduly high.
FIGS. 5A-5C schematically illustrate specific examples of output images obtained by the above exposure control methods.
FIG. 5A shows an ideal exemplary image that was taken so as to have a wide dynamic range. Indoor objects (a wall 10, etc.) as low-luminance objects and an outdoor scene (a tree 20, etc.) as high-luminance objects are both imaged properly.
In contrast, in the case of FIG. 5B, since the exposure control method (1) (adjusted to the high-luminance objects) was employed, the indoor objects (wall 10, etc.) as the low-luminance objects are blacked because of insufficient light quantities. In the case of FIG. 5C, since the exposure control method (2) (adjusted to the low-luminance objects) was employed, the white levels of the outdoor scene (tree 20, etc.) as the high-luminance objects are unduly high.